Two projects relating to the regulation of protein synthesis in chick oviduct, an estrogen-dependent tissue, are being pursued. The first is an investigation of the mechanism of protein synthesis initiation. Ovalbumin messenger RNA has been isolated from hen oviduct polysomes and will be labeled by chemical techniques with a radioisotope. This will then be used as a probe to follow the steps of protein synthesis initiation with particular interest in mRNA-recognizing proteins (initiation factors, poly(A)-binding proteins, etc.). A second project is concerned with what factors affect and regulate mRNA stability in oviduct. The hypothesis to be tested is that since ovalbumin is synthesized on bound polysomes, the mRNA is less available to soluble nucleases and is therefore more stable than the average mRNA. Techniques will be developed for measuring half-life of ovalbumin mRNA in vivo and determining if this is affected by the intracellular location of the polysomes.